DE3026010C2 - Production of propylene-ethylene copolymers - Google Patents

Description

a) an aluminum trialkyl compound, which is optionally at least partially present as a complex with an electron donor compound, and

b) Tltan tri or tetrahalide or a complex of a titanium tri or tetrahalide with an electron donor compound, each on a magnesium halogenide carrier,

is used.

2. The method according to claim 1, characterized in that the polymerization is carried out at a temperature in the range of 51 to 69 ⁰ C.

The continuous polymerization of propylene under an adequate pressure to keep at least a portion of the propylene in the liquid phase is known in the art. The catalyst system used in the past in such a polymerization consists of a titanium halogen component which has not been modified or modified with an electron donor and which has been activated with an aluminum-luminescent cocatalyst. Typical examples of conventional propylene polymeric catalyst systems include carbonized titanium chloride / aluminum aluminum catalysts of the general formula η TlCl ₁ · AlCl ₃ which have been activated with diethylaluminum chloride or triethylaluminum. The co-krlstalll slerte Tltantrichlorld - Aluminlumtrlchlorld can a modlfizlerungsbehalt with a suitable electric donor compound in order to increase its activity or stereospecificity. Such Connections are e.g. B. phosphorus compounds, esters of inorganic and organic acids, ethers and numerous other compounds. The FR-PS 14 77 315 describes a process for the polymerization of propylene, the 0.5 to 3 wt .- 96 Ethy len are admixed using such conventional catalyst systems. With conventional Catalysts are obtained but in general an unfavorable effect when introducing ethylene into the Charging at temperatures above 60 ° C, with productivity values being achieved that are lower than those obtained in the absence of ethylene and at optimal polymerization temperatures.

Recently, new catalysts have been developed that are far more active than the aforementioned conventional

Chen catalysts for the polymerization of α-olefins are. In short, these catalysts contain one Titanium halogen catalyst component on a magnesium halide as support and an alkyl aluminum compound, which can be present as a complex with an electron donor veneer.

These catalyst components are described in the patent literature, e.g. 41 15 319, has been described.

From DE-OS 25 05 825 is a process for the production of copolymers from ethylene and propylene Known in the presence of such catalysts, in which, however, the propylene content is not 90% by weight exceeds.

It is known that in the polymerization of propylene in the presence of a liquid monomer the Efficacy (productivity) of each of the said catalyst systems is increased when the temperature is raised to a

so the level of about 68 ° C or about higher is raised, with maximum productivity values being achieved. Typical catfish results in a temperature rise of about 51 ° C to about 68 ⁰ C in almost a doubling of the catalyst activity, regardless of the specially selected catalyst system. A further increase in temperature causes a rapid drop in productivity from the maximum values. There is therefore a for each catalyst system used in the propylene liquid polymer solution Relatively high temperatures and pressure (to ensure the liquid phase at the temperature) to achieve maximum productivity level. Setting these optimal process conditions contributes to a part to general process costs in the form of equipment for increased preheating, cooling and pressure requirements. The object of the present invention is therefore to create a process for the production of polypropylene,

^w) that the disadvantages just described of the previously known processes are reported and, in particular, the catalyst productivity is significantly improved.

The subject matter of the invention is defined by the above claims.

I) Ic / dehnung / elgi comparatively the improved results obtained with the invention-based seduction Results.

^hs Uncrwariclerwclsc was found that adding a small amount of ethylene to Propylenbeschlkkung using the catalyst system described above Dall a dramatic and totally unexpected increase in Katalysatorproduktlvltat result has. It was further found that the increase in productivity does not depend on any particular value of the ethylene concentration in the total charge.

but that any amount within a range of 0.5 to 1.7 weight percent is about the same improvement causes. In addition, it is very important that it has been found that in the presence of ethylene in the monomer feed the effect of temperature on catalyst productivity is eliminated, d. H. the increased catalyst productivity remains essentially constant over a wide temperature range.

These results are in direct contradiction to what happens with the same procedure when adding ethylene for propylene loading, but occurs with conventional, unsupported titanium catalyst systems. With these Temperature is the main factor influencing productivity. Although at temperatures below the optimal temperatures the presence of ethylene sometimes slightly increases productivity; i. H. around 10% or less, appears to increase. However, no fail has occurred in which the presence of ethylene in the propylene filling brought about a better productivity than that which one in the absence of ethylene In the charge and at the optimum polymerization temperature (that is 68 ° -71 ° C) to achieve maximum Productivity received.

Before the process according to the invention is carried out, the liquid phase reactor can only operate with propylene monomer be driven, d. H. Carrying out a homopolymerization at a temperature between 46 ° and 74 ° C, the productivity obtained being measured at each temperature level. So you can get the catalyst productivity in relation to the temperature.

The catalyst components used in the invention can be such as. B. the recently developed, highly active magnesium halide supported catalyst components *) and organoaluminum cocatalyst components how they z. B. in US? S 39 53 414, 40 51 313, 41 15 319 and 38 30 787 have been described, the disclosure of which is expressly referred to here.

Such a catalyst composition is typically a two-component composition, wherein the components are introduced separately into the polymerization reactor. Component a) such The composition is selected from the group of the alkylaluminum compounds with suitably 1-8 carbon atoms In the alkyl group selected such. B. Trläthylaluminium, Trlmethylaluminlum, Trl-n-butylaluminium, Trilsobutylaluminum, Trilsohexylaluminum, Trl-n-octylaluminum and Trilsooctylaluminum. It but can also, for example, tripropylaluminum, trimethylaluminum and trheptylaluminium used where the alkyl groups can be straight or branched chain. The Trlalkylaluminum is before Introducing Complexed into the polymerization reactor with an electron donor. the The best results are achieved when the electron donors are esters of carboxylic acids, especially esters aromatic acids or diamines can be used.

Some typical examples of such compounds are methyl and ethyl benzoate, methyl and ethyl pmethoxybenzoate, Diethyl carbonate, ethyl acetate, methyl maleate, triethyl borate, ethyl o-chlorobenzoate, ethyl naphthenate, Methyl p-toluate, ethyl toluate, ethyl p-butoxybenzoate, ethyl cyclohexanoate, ethyl pivalate, Ν, Ν, Ν ', Ν'-tetramethylendlamln, 1,2,4-Trimethylpperazln and 2,5-Dimethylpperazln. The molar ratio of aluminum alkyl to the electron donor can expediently between 1 and 100, preferably between 2 and 5 be. Solutions of electron donors and the triacylaluminium compound in a hydrocarbon, such as B. hexane or heptane, are preferred for a particular tent, which is generally less than 1 hour, reacted beforehand before the mixture is added to the polymerization reactor.

The other component of the catalyst composition is either a Tltantrl or Tetrahalogenld a magnesium halide carrier or a complex of a titanium tri- or tetrahalide with an electron donor compound on a magnesium halide support. The contained in the respective halide Halogen can be chlorine, bromine or iodine, the preferred halogen being chlorine. If to form the Complex an electron donor compound is used, this comes appropriately from the Group of esters of inorganic or organic oxygen-containing acids and polyamines. Examples of such Compounds are the esters of aromatic carboxylic acids, such as. B. benzoic acid, p-methoxybenzoic acid and p-toluic acid, and in particular the alkyl esters of the acids mentioned; also the alkylene lamellas, such as. B. N ', N ', N ", N" -Tetramethyläthylendlamln.

The molar ratio of magnesium to the electron donor is expediently 1 or more than 1, preferably between 2 and 10. In general, the titanium content, expressed as titanium metal, is between 0.1 and 20% by weight in the supported catalyst component, preferably between 1 and 3% by weight.

The preparation of such supported catalyst components has been described in the literature and these are available on the market.

In specific embodiments of the invention, the acid component contains as electron donors used esters between 1 to 11 carbon atoms!:, while the alcohol component in particular 1 to 2 Has carbon atoms. If a diamine compound is used for this purpose, it contains S5 preferably 4 to 7 carbon atoms.

The catalyst components a) and b) are introduced into the reaction zone in such amounts that the Molar ratio of Al / Tl in a wide range of expediently about 1 to 10,000, preferably between 10 until 200 is held.

The polymerization process used in the present invention is the known liquid phase process, wherein the propylene acts as both a liquid diluent and a reaction driver, with the exception of small amounts of inert hydrocarbons, such as. B. hexane, mineral oils, etc., the introduction of the Catalyst component can be used in the reaction zone. The used according to the invention Reaction conditions include polymerization temperatures in the range of 46 ° to 74 ° C, preferably 51 ° up to 69 ° C. The pressure should be increased sufficiently to remove at least part of the propylene In the liquid phase f> 5 to keep. A suitable pressure is 14 atmospheres and more, in particular up to 35 atmospheres.

*) is meant here and in the following the component b)

The total solids present in the reaction zone according to this system is usually 15 to 20%, although obviously lower or higher values, e.g. B. up to 60% polymer solids, may be present. For convenient handling of the slurry, polymerization is used preferably kept in the range of the above solids values. The reaction is continuous; H. the monomer feed (i.e. propylene and ethylene) and the catalyst components are continuously fed into the reactor tor, and a slurry of the polymer product and the liquid propylene are preferably present withdrawn by means of a cyclic Entnahmeventlls, which simulates the continuous operation. Optionally, various modifying agents, such as. B. hydrogen, may be added to change the properties of the polymer product. Such modifiers are known in the art are known and do not need to be further described since they are not part of this invention.

The withdrawn polymer slurry is transferred to a zone of lower pressure, e.g. B. 3.5 atmospheres or less, passed (ie in a zone whose pressure is lower than in the polymerization reaction) where, due to the pressure drop and the volatile nature of the Polymerisatlonsbestandtelle a flash evaporation of these volatile components from the solid polymer occurs. This flash evaporation, which can be assisted by heating, results in a polymer powder that is substantially dry, this formulation denoting a polymer that contains 5% or less volatiles. After this low pressure flash evaporation zone, the non-circulating monomer stream is subjected to an overhead distillation and at least a portion of it is compressed and condensed and returned to the reactor. The polymer can then, if appropriate, be reacted further in a subsequent polymerization zone or also be passed directly to a final drying zone in order to remove the remaining volatile constituents.

Alternatively, the liquid polymerization medium can be filtered and centrifuged under pressure, and that

liquid propylene can (after appropriate flushing) be fed back into the reactor for this purpose

Save energy for re-compressing. This process has the advantage that certain soluble

^2S impurities (the aluminum alkyl compounds and organic esters) are removed from the polymer.

This in turn results in a polymer product with a lower residue content.

Due to the generally high productivity of the supported catalyst system, the in kg of polymer produced per kg titanium metal is calculated - whereby the productivity is further increased according to the invention - there is none Need to remove the catalyst residues from the polymer by ash removal, as is the case with conventional catalyst is the case.

The polymer products obtained according to the invention are essentially crystalline propylene polymers, the

have improved impact strength and brittle temperatures due to the small amount of ethylene, without adversely affecting the desired properties of the propylene homopolymer. The end use The polymer products include injection molding processes for housewares and containers, blow molding processes of

Bottles, extrusion processes for packaging filaments, etc. The following examples serve to explain the invention in more detail. Examples 1 to 5 and comparative experiments A to E.

The experiments were carried out on a larger scale in a continuous pilot plant, with monomer and catalyst components being continuously introduced into a reactor with stirring. the The rate of monomer feed corresponded to a residence time in the reactor of 2 hours. the The organoaluminum compound of the catalyst system was a hexane solution of trisobutylaluminum (TIBA), which before being introduced into the reactor with a hexane solution of methyl p-toluate (MPT), an elec-

«Tron donor connection, had been dealt with. The solid supported titanium halide catalyst component was a catalyst available on the market. The supported catalyst component contained 1.5% by weight of titanium, 3% by weight Magnesium, 60% by weight of chlorine and 9.6% by weight of volatile hydrocarbons. Ethyl benzoate has been used in preparing the supported catalyst component. The two catalyst components were in one Speed added, which was directly proportional to the polymer production rate and in sufficient

amounts sufficient to maintain a nominal 40% polymer solids concentration in the reactor slurry. The catalyst productivity (kg polymer / kg Tl metal) was in each case Due to the polymer slurry withdrawal fluctuates, the solids contents in the slurry and the rate of addition of the titanium catalyst component is calculated. The process conditions used and the results are given in Table I.

Table II presents the same data which show in a somewhat modified form. The comparison value (100% efficiency) for the data is the average catalyst productivity at 68 ⁰ C and 0% Äthylenzugabe. The average catalyst effectiveness values in the tests at the respective other temperatures were obtained by specifying the productivity values observed as a percentage of the average comparative productivity.

The data is also shown in the drawing. Table I.

Example or
Comparative experiment

Reactor temperature

⁰ C "

Reaklore

pressure

aiii

Älhylen

Wt%

Mole ratio

MoI ratio

ΤΙΒΛ / ΜΡΤ ΛΙ / Τί

productivity

1000 kg / kg Ti

% Ethylene incorporation in Polvmeren

comparison Λ 68 example 1 68 Mountain comparison B. 68 comparison C. 68 Example 2 68 comparison D. 54 Example 3 54 Example 4 54 comparison E. 52 Example 5 52

30.9 0 31.1 0.9 31.6 1.8 30.7 0 31.9 1.4 23.8 0 24.4 U 24.2 1.1 22.4 0 22.9 1.6

2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.1

152

152

152

40

40

75

75

150

150

150

376 411 449 394 513 268 498 551 215 433

1.5

3.0

2.7

2.4

2.4

3.7

Table II

Example or comparison attempt

Ethylene temperature catalyst efficiency ° C%

Comparison A and C (average value) no 80 100 Examples 1 and 2 (average value) Yes 68 119 Comparison D no 54 70 Examples 3 and 4 (average value) Yes 54 136 Comparison E no 52 56 Example 5 Yes 52 112 '

') Catalyst effective wedge low due to a low ratio of Τ1ΒΛ / ΜΡΤ (2.1 compared to 2.8 in all other attempts)

As can be seen from the data shown in the drawing, the addition of small amounts is effective from ethylene to propylene a dramatic increase in catalyst efficiency (productivity) Beyond those that can be achieved at the optimum temperature without the addition of ethylene. Also is there Effect of temperature switched off, d. H. the improved productivity value is substantially above constant over a wide temperature range of 52 to 68 ° C.

Comparative experiments F to L

The same procedure as described above was repeated, but the catalyst systems failed two similarly strong, conventional, unsupported titanium trichloride catalysts activated with an electron donor compound and diethylaluminium chloride as cocatalyst.

The corresponding test data are given in Tables HI and IV. As can be seen from this data. the Produktlvltätswerte in the presence of ethylene in all cases, were lower than those that were obtained at about the optimum temperature conditions (68 ⁰ C) In the absence of ethylene, uie Poiymerisationstemperatur had a considerable effect on the Produktlvltätswerte.

Table HI Ethylene temperature Catalyst- Comparative experiment effectiveness ⁰ C % no 68 100 Compare F Yes 66 97 Comparison G Yes 60 96 Compare H Yes 54 81 Comparison I. no 66 88 Comparison K Yes 66 96 Compare L

Table IV

Comparative experiment reactor temperature 5 ° C

Reactor pressure ethylene atü wt .-%

Mole productivity% ethylene Ratio in the polymer

ΛΙ / Ti kg / kg Kalalys.

Comparison F ¹ ) 68 30.8 0 3.0 1160 0 Comparison G ¹ ) 66 29.3 0.9 3.0 1125 3.8 i "comparison H ¹ ) 60 26.3 0.9 3.0 1118 3.6 Comparison I ¹ ) 54 24.1 1.4 3.0 937 4.5 Comparison K ² ) 66 30.2 0 3.0 1023 0 lh '; Comparison L ² ) 66 30.8 1.0 3.0 1115 2.7

') Commercially available analyzer (3 TiCh ■ AICh modified with electron donor) ^) Hybrid from the commercially available catalysts (with electron donor modified 3 T1CI3 ■ Aldi) (unmodified 3 T1CI3 ■ AICI3)

20th

25th

30th

Comparative experiments M to

A commercially available, non-activated TICI ₃ • AlClJ catalyst at the conditions shown in Table V was used in these experiments. Table V shows that no improvements beyond optimal productivity were obtained in these experiments.

Table V Comparative experiment

Ethylene

Temperature ⁰ C

Catalyst efficiency

Compare M no 68 Comparison N. no 60 Comparison O Yes 60

100 70 80

Table Vl

40 comparison test

Reactor-

temperalur

⁰ C

Reactor pressure ethylene atü wt .-%

Mole ratio Ai / Ti

productivity

kg / kg Kalalys.

% Ethylene in the polymer

45

Compare M 68 Comparison N. 60 Comparison O 60

30.8 25.6 26.0

0 0 0.9

3.65 3.65 3.65

1275

890

1015

0 0 3.3

50

Ml

65

Comparative experiments P to R

The catalyst used in this series of experiments was a phosphorus oxychloride-modified one 3TlCl] · AlClj catalyst with methylaluminum chloride as cocatalyst. Even with this conventional one Catalyst, no improvements beyond optimal productivity were obtained, as shown in the data In 55 Tables VII and VIII can be obtained.

Table VI Comparative experiment

Ethylene

Temperature ⁰ C

Comparison P no Compare Q and R yes

(Average value)

Catalytic wedge

100 49

reactor 30 26 010 Wt% Molar productivity % Ethylene Table VIII temperature 0 relationship in the polymer Comparative experiment ⁰ C Reactor pressure ethylene 1.3 Al / Ti kg / kg cat. 68 1.3 3.0 1480 0 54 alü 3.0 7 <> 6 2.5 Compare P 54 30.8 3.0 664 4.0 Comparison Q 25.2 1 sheet of drawings Comparison R 25.2

if SS

Claims (1)

Patent claims: 1. Continuous process for the production of propylene-ethylene Mlschpolymerlsaten by polymerization of a Propylenbeschlckung, which 0.5 to 1.7 wt .- * (based on the weight of the propylene) of ethylene s len, at a temperature in the range of 46 to 74 ° C and at sufficient pressure to keep the To keep propylene in the liquid phase in the polymerization zone, in the presence of a catalyst composition based on a Tltanhalogenldverblndung activated with an organoaluminum reducing agent, characterized in that a catalyst composition with the following components: